With the rise of handheld augmented reality (AR) systems for mobile platforms, such as cellphones, sensors have become increasingly important. Many current AR applications on mobile platforms rely on the built-in sensors to overlay registered information over a video background. The built-in sensors used for example include satellite position system (SPS Receivers), magnetic compasses, and linear accelerometers. Unfortunately, commercial mobile platforms typically use inexpensive and low-power MEMS devices resulting in relatively poor performance compared to high quality sensors that are available.
Magnetometers, as used in magnetic compasses, and accelerometers provide absolute estimations of orientation with respect to the world reference frame. Their simple use makes them a standard component in most AR systems. However, magnetometers suffer from noise, jittering and temporal magnetic influences, often leading to substantial deviations, e.g., 10 s of degrees, in the orientation measurement. While dedicated off-the-shelf orientation sensors have improved steadily over time, commercial mobile platforms typically rely on less accurate components due to price and size limitations. Accordingly, AR applications in commercial mobile platforms suffer from the inaccurate and sometimes jittering estimation of orientation.
Vision-based tracking systems provide a more stable orientation estimation and can provide pixel accurate overlays in video-see-through systems. However, visual tracking requires a model of the environment to provide estimates with respect to a world reference frame. In mobile applications, visual tracking is often performed relative to an unknown initial orientation rather than to an absolute orientation, such as magnetic north. Consequently, vision-based tracking systems do not provide an absolute orientation in an uninformed environment, where there is no prior knowledge of the environment.
Thus, improvements are needed for mapping and tracking of a mobile platform in an uninformed environment that provides an absolute orientation with respect to the world reference frame.